1. Field of the Invention
The present invention relates to a disk storage device for storing digital recording data on a disk using an optical beam emitted from an optical head. Particularly, the present invention relates to a disk storage device that can write additional data onto a disk while maintaining continuity of recording data.
2. Description of Related Art
CD-R (Compact Disk-Recordable) drives or CD-RW (Compact Disk-ReWritable) drives of the CD (Compact Disk) family are well known disk storage systems for recording digital data onto a disk using an optical beam emitted from an optical head.
During recording of CD-R and CD-RW disks, the recording device may stop the recording operation when a buffer under-run error occurs because of recording speed or data stream conditions which interrupt creation of data to be stored onto a disk.
Upon a halt of the recording operation, a single use disk such as a CD-R disk becomes unusable.
In the case of an rewritable disk such as a CD-RW disk, when a recording operation is ceased, all data must be rerecorded from the beginning. Here, there is the problem in that the re-procedure is troublesome and a waste time occurs.
There is known a packet write system in which data is recorded in packet units. However, because this packet write system is not necessarily supported by the CD-ROM, it is desirable to record data one track at a time or one session at a time, in terms of compatibility with CD systems.
The packet write system requires forming seven joint blocks for connection between packets. Hence, there is the problem in that the recording capacity of a disk is wasted.
For that reason, if recording data can be continuously and seamlessly added to data already recorded on a disk prior to halt of recording, track-at-a-time or the session-at-a-time systems are preferable because of increased compatibility with CD-ROM drivers. Moreover, in terms of an effective use of the recording capacity of a disk, a recording system such as the packet write system that requires joint blocks is disadvantageous because of the additional writing required. Hence, there has long been demand for disk recording devices that can additionally write continuously and without any joint blocks.
When additional data are written continuously as described above, it is necessary that the beginning of additional data to be recorded be seamlessly connected to the end of the data already recorded. However, it has been difficult to seamlessly and continuously connect sets of data.
When an optical head directs a laser onto a disk to record data onto the disk, it is difficult to accurately match the position where data recording on the disk starts with the end of data already recorded. This results from the time between the time an instruction for an additional writing operation is issued and the time the strength of the laser reaches a level necessary for recording. Moreover, it is difficult to accurately terminate at a break of recorded data at the time of ceasing a recording operation. Further, there will often be differences between the level when recording was halted and the level when recording is resumed. Therefore, merely joining the end of recorded data with the beginning of additional data to be written is unsatisfactory.
This invention is made to overcome the above-described problems. It is an object of the present invention to provide a disk storage device that can continuously execute additional writing in such a way that the beginning of recording data to be additionally written is substantially and seamlessly joined with the end of data already recorded.
According to the present invention, when the record decision unit judges that there has been an interruption of recording, recording data in a predetermined frame is terminated. After data is continuously recorded onto a disk until the duration of a frame synchronous signal following the predetermined frame, the control output generated from the head output control circuit is controlled to cease the recording operation. Meanwhile, when the record decision unit judges the start of recording, the control output generated from the head output control circuit is controlled to initiate recording onto the disk from the frame synchronous signal duration for which recording data onto the disk is ceased. Thus, when recording data is additionally written onto the disk used when a halt of recording occurs, in continuous with the recorded data, the joint portion between the end of the recorded data and the beginning of the recording data for additional writing acts as a frame synchronous signal duration. This facilitates management of data for which recording is stopped or started. Moreover, since the recorded data are jointed at the predetermined data structure portion, it is very unlikely that the seam caused by the additional writing will adversely affect data retrieval or use.